Physical Constraint Preserving Higher Order Finite Volume Schemes for Divergence-Free Astrophysical MHD and RMHD

Fuente: arXiv
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Main Authors: Balsara, Dinshaw S., Bhoriya, Deepak, Singh, Chetan, Kumar, Harish, Käppeli, Roger, Gatti, Federico
Format: Preprint
Published: 2025
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author Balsara, Dinshaw S.
Bhoriya, Deepak
Singh, Chetan
Kumar, Harish
Käppeli, Roger
Gatti, Federico
author_facet Balsara, Dinshaw S.
Bhoriya, Deepak
Singh, Chetan
Kumar, Harish
Käppeli, Roger
Gatti, Federico
contents Higher order finite volume schemes for magnetohydrodynamics (MHD) and relativistic magnetohydrodynamics (RMHD) are very valuable because they allow us to carry out astrophysical simulations with very high accuracy. However, astrophysical problems sometimes have unusually large Mach numbers, exceptionally high Lorentz factors and very strong magnetic fields. All these effects cause higher order codes to become brittle and prone to code crashes. In this paper we document physical constraint preserving (PCP) methods for treating numerical MHD and RMHD. While unnecessary for standard problems, for stringent astrophysical problems these methods show their value. We describe higher order methods that allow divergence-free evolution of the magnetic field. We present a novel two-dimensional Riemann solver. This two-dimensional Riemann solver plays a key role in the design of PCP schemes for MHD and RMHD. We present a very simple PCP formulation and show how it is amalgamated with the evolution of face-centered magnetic fields. The methods presented here are time-explicit and do not add much to the computational cost. We show that the methods meet their design accuracies and work well on problems that would otherwise be considered too extreme for typical higher order Godunov methods of the type used in computational astrophysics.
format Preprint
id arxiv_https___arxiv_org_abs_2506_11181
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Physical Constraint Preserving Higher Order Finite Volume Schemes for Divergence-Free Astrophysical MHD and RMHD
Balsara, Dinshaw S.
Bhoriya, Deepak
Singh, Chetan
Kumar, Harish
Käppeli, Roger
Gatti, Federico
Instrumentation and Methods for Astrophysics
High Energy Astrophysical Phenomena
Numerical Analysis
Computational Physics
Higher order finite volume schemes for magnetohydrodynamics (MHD) and relativistic magnetohydrodynamics (RMHD) are very valuable because they allow us to carry out astrophysical simulations with very high accuracy. However, astrophysical problems sometimes have unusually large Mach numbers, exceptionally high Lorentz factors and very strong magnetic fields. All these effects cause higher order codes to become brittle and prone to code crashes. In this paper we document physical constraint preserving (PCP) methods for treating numerical MHD and RMHD. While unnecessary for standard problems, for stringent astrophysical problems these methods show their value. We describe higher order methods that allow divergence-free evolution of the magnetic field. We present a novel two-dimensional Riemann solver. This two-dimensional Riemann solver plays a key role in the design of PCP schemes for MHD and RMHD. We present a very simple PCP formulation and show how it is amalgamated with the evolution of face-centered magnetic fields. The methods presented here are time-explicit and do not add much to the computational cost. We show that the methods meet their design accuracies and work well on problems that would otherwise be considered too extreme for typical higher order Godunov methods of the type used in computational astrophysics.
title Physical Constraint Preserving Higher Order Finite Volume Schemes for Divergence-Free Astrophysical MHD and RMHD
topic Instrumentation and Methods for Astrophysics
High Energy Astrophysical Phenomena
Numerical Analysis
Computational Physics
url https://arxiv.org/abs/2506.11181